1. Field of the Invention
The present invention relates generally to a satellite receiver system, and in particular, to an alignment method for multi-band consumer receiver antennas.
2. Description of the Related Art
Satellite broadcasting of communications signals has become commonplace. Satellite distribution of commercial signals for use in television programming currently utilizes multiple feedhorns on a single Outdoor Unit (ODU) which supply signals to up to eight IRDs on separate cables from a multiswitch.
FIG. 1 illustrates a typical satellite television installation of the related art.
System 100 shows an embodiment of a system using signals sent from Satellite A (SatA) 102, Satellite B (SatB) 104, and Satellite C (SatC) 106 (with transponders 28, 30, and 32 converted to transponders 8, 10, and 12, respectively) as well as other satellites using Ka-band signals that are typically located at the 99 and 103 orbital slots, that are directly broadcast to an Outdoor Unit (ODU) 108 that is typically attached to the outside of a house 110. ODU 108 receives these signals and sends the received signals to IRD 112, which decodes the signals and separates the signals into viewer channels, which are then passed to television 114 for viewing by a user. There can be more than one satellite transmitting from each orbital location. Orbital locations are also known as “orbital slots” and are referred to as both “orbital locations” and “orbital slots” herein.
Satellite uplink signals 116 are transmitted by one or more uplink facilities 118 to the satellites 102-106 that are typically in geosynchronous orbit. Satellites 102-106 amplify and rebroadcast the uplink signals 116, through transponders located on the satellite, as downlink signals 120. Depending on the satellite 102-106 antenna pattern, the downlink signals 120 are directed towards geographic areas for reception by the ODU 108.
Each satellite 102-106 typically broadcasts downlink signals 120 in typically thirty-two (32) different sets of frequencies, often referred to as transponders, which are licensed to various users for broadcasting of programming, which can be audio, video, or data signals, or any combination. These signals have typically been located in the Ku-band Fixed Satellite Service (FSS) and Broadcast Satellite Service (BSS) bands of frequencies in the 10-13 GHz range and in the Ka-band FSS band of 18-21 GHz.
FIG. 2 illustrates a typical ODU of the related art.
In another embodiment, ODU 108 typically uses reflector dish 122 and feedhorn assembly 124 to receive and direct downlink signals 120 onto feedhorn assembly 124. Reflector dish 122 and feedhorn assembly 124 are typically mounted on bracket 126 and attached to a structure for stable mounting. Feedhorn assembly 124 typically comprises one or more Low Noise Block converters 128, which are connected via wires or coaxial cables to a multiswitch, which can be located within feedhorn assembly 124, elsewhere on the ODU 108, or within house 110. LNBs typically downconvert the FSS and/or BSS-band, Ku-band, and Ka-band downlink signals 120 into frequencies that are easily transmitted by wire or cable, which are typically in the L-band of frequencies, which typically ranges from 250 MHz to 2150 MHz. This downconversion makes it possible to distribute the signals within a home using standard coaxial cables.
The multiswitch enables system 100 to selectively switch the signals from SatA 102, SatB 104, and SatC 106, and deliver these signals via cables 124 to each of the IRDs 112A-D located within house 110. Typically, the multiswitch is a four-input, four-output (4×4) multiswitch, where two inputs to the multiswitch are from SatA 102, one input to the multiswitch is from SatB 104, and one input to the multiswitch is a combined input from SatB 104 and SatC 106. There can be other inputs for other purposes, e.g., off-air or other antenna inputs or for other LNBs receiving services from satellites at other orbital locations, without departing from the scope of the present invention. The multiswitch can be other sizes, such as a 6×8 multiswitch, if desired. SatB 104 typically delivers local programming to specified geographic areas, but can also deliver other programming as desired.
To maximize the available bandwidth in the Ku-band and Ka-band of downlink signals 120, each broadcast frequency is further divided into polarizations. Each LNB 128 can receive both orthogonal polarizations at the same time with parallel sets of electronics, so with the use of either an integrated or external multiswitch, downlink signals 120 can be selectively filtered out from travelling through the system 100 to each IRD 112A-D.
IRDs 112A-D currently typically use a one-way communications system to control the multiswitch. Each IRD 112A-D has a dedicated cable 124 connected directly to the multiswitch, and each IRD independently places a voltage and signal combination on the dedicated cable to program the multiswitch. For example, IRD 112A may wish to view a signal that is provided by SatA 102. To receive that signal, IRD 112A sends a voltage/tone signal on the dedicated cable back to the multiswitch, and the multiswitch delivers the satA 102 signal to IRD 112A on dedicated cable 124. IRD 112B independently controls the output port that IRD 112B is coupled to, and thus may deliver a different voltage/tone signal to the multiswitch. The voltage/tone signal typically comprises a 13 Volts DC (VDC) or 18 VDC signal, with or without a 22 kHz tone superimposed on the DC signal. 13 VDC without the 22 kHz tone would select one port, 13 VDC with the 22 kHz tone would select another port of the multiswitch, etc. There can also be a modulated tone, typically a 22 kHz tone, where the modulation schema can select one of any number of inputs based on the modulation scheme. For simplicity and cost savings, this control system has been used with the constraint of 4 cables coming for a single feedhorn assembly 124, which therefore only requires the 4 possible state combinations of tone/no-tone and hi/low voltage.
To reduce the cost of the ODU 108, outputs of the LNBs 128 present in the ODU 108 can be combined, or “stacked,” depending on the ODU 108 design. The stacking of the LNB 128 outputs occurs after the LNB has received and downconverted the input signal. This allows for multiple polarizations, one from each satellite 102-106, to pass through each LNB 128. So one LNB 128 can, for example, receive the Left Hand Circular Polarization (LHCP) signals from SatC 102 and SatB 104, while another LNB receives the Right Hand Circular Polarization (RHCP) signals from SatB 104, which allows for fewer wires or cables between the feedhorn assembly 124 and the multiswitch.
The Ka-band of downlink signals 120 will be further divided into two bands, an upper band of frequencies called the “A” band and a lower band of frequencies called the “B” band. Once satellites are deployed within system 100 to broadcast these frequencies, the various LNBs 128 in the feedhorn assembly 124 can deliver the signals from the Ku-band, the A band Ka-band, and the B band Ka-band signals for a given polarization to the multiswitch. However, current IRD 112 and system 100 designs cannot tune across this entire resulting frequency band without the use of more than 4 cables, which limits the usefulness of this frequency combining feature.
By stacking the LNB 128 inputs as described above, each LNB 128 typically delivers 48 transponders of information to the multiswitch, but some LNBs 128 can deliver more or less in blocks of various size. The multiswitch allows each output of the multiswitch to receive every LNB 128 signal (which is an input to the multiswitch) without filtering or modifying that information, which allows for each IRD 112 to receive more data. However, as mentioned above, current IRDs 112 cannot use the information in some of the proposed frequencies used for downlink signals 120, thus rendering useless the information transmitted in those downlink signals 120. Typically, an antenna reflector 122 is pointed toward the southern sky, and roughly aligned with the satellite downlink 120 beam, and then fine-tuned using a power meter or other alignment tools. The precision of such an alignment is usually not critical. However, additional satellites have been deployed that require more exacting alignment methods, and, without exacting alignment of the antenna reflector 122, the signals from the additional satellites will not be properly received, rendering these signals useless for data and video transmission.
FIG. 2A illustrates another embodiment of an ODU of the related art.
Another embodiment of ODU 108 uses a Single Wire Multiswitch (SWM) ODU system 130. Rather than having a dedicated cables from ODU 108 for each IRD 112A-D, e.g., one cable per IRD 108, system 130 uses a single cable 132 from ODU 108 to a splitter 134, and then directs individual cables 136-142 from splitter 134 to various types of IRDs 112A-D. Splitter 134 is typically located within the home, so only one cable 132 needs to enter the home to provide the signals from SWM ODU 108 for all IRDs 112A-D present in a given residence. For example, in one embodiment, IRD 112A can be a single tuner Standard Definition (SD) IRD, while IRD 112B can be a two-tuner SD Digital Video Recorder (DVR). Further, both SD and High Definition (HD) signals can be sent in system 130, such that both SD and HD signals can be sent through splitter 134 to various IRDs 112A-D. In the same embodiment as described above, IRD 112C can be a single tuner HD IRD, and IRD 112D can be a two-tuner HD DVR. Other combinations of IRDs 112A-D, with SD, HD, or combinations of SD and HD signals, can be accommodated by system 130.
System 130 allows for reduced installation complexity and lowers cost. Downlink signals 120 from satellites 102-106 are received at the SWM ODU 108 in the same manner as described with respect to FIG. 2. However, system 130 typically uses Frequency Shift Keyed (FSK) commands with a signal splitter 134 to allow for two-way communications between the ODU 108 and the various IRDs 112A-D. Other types of command structures can be used in different embodiments of system 130 if desired. The system 130 allocates a transponder channel for each connected IRD 112A-D. There are typically eight distinct programming channels available for use by the various IRDs 112A-D, however, a larger or smaller number of channels can be made available if desired. The SWM system 130 allocates one channel to single tuner IRDs 112A-D and two channels for two-channel (DVR)-based IRDs 112A-D. Each IRD 112A-D sends messages to the SWM ODU 108 requesting a desired transponder for viewing, and the SWM ODU 108 circuit receives similar requests from all connected and active IRDs 112A-D. The SWM ODU 108 then selects or “plucks” the receiver requested transponder from the received downlink signals 120, locates the selected transponder signal in the allocated channel for the requesting IRD 112-A-D, and aggregates all of the selected transponder channels for active IRDs 112A-D for transmission using single cable 132.
It can be seen, then, that there is a need in the art for an alignment method for a satellite broadcast system that can be expanded to include new satellites and new transmission frequencies.